Vascular access is important for the treatment of some chronic diseases such as those requiring hemodialysis treatments. A vascular access site should be prepared before starting those kinds of treatments. Doing this allows for easier removal and replacement of the patient's blood during treatment. The access site should allow for continuous, high blood-flow volumes. Common complications from vascular access sites include infection and low blood flow caused by blood clotting in the access passageway.
Arteriovenous (AV) fistulas or AV grafts are basic kinds of vascular access for hemodialysis. An AV fistula connects an artery to a vein in a patient (such as in the patient's forearm) and is useful because it causes the vein to grow larger and stronger allowing easier access to the blood system. The AV fistula is considered the best long-term vascular access for hemodialysis because it provides adequate blood flow, lasts a long time, and has a lower complication rate than other types of access. If an AV fistula cannot be created, an AV graft or venous catheter may be needed.
An AV fistula requires planning because it takes time after surgery to develop—usually several months. But properly formed fistulas are less likely to form clots or become infected than are other access methods. Also, properly formed fistulas may work longer than other kinds of access—sometimes for years.
A synthetic arteriovenous graft is another type of vascular access. It connects an artery to a vein using a synthetic tube, or graft, implanted in the patient's forearm, for example. The graft becomes an artificial vein that can repeatedly receive a needle for blood access during hemodialysis. A graft can be used sooner than an AV fistula—2 or 3 weeks after placement.
Compared with properly formed fistulas, grafts have more clotting and infection problems and need more frequent replacement.
But using vascular grafts as described above changes the circulatory system. The changes caused by the placement of vascular grafts and by the creation of vascular anastomoses or fistulas sometimes cause the circulatory system near the graft, fistula, or anastomosis to develop abnormal shear or circumferential stresses. Moreover, the changes sometimes alter blood pressure, blood flow, and other hemodynamic factors. And the changes can cause torsional stress in the vasculature of or near the graft, fistula, or anastomosis.
What is needed is a device that regulates blood flow and shear stress by limiting the outward expansion of the artery or vein in question, alleviates circumferential wall stress problems, and tethers the affected vessels substantially in place or provides any one or any combination of these benefits.